Willey was left brain-dead after a 17-year-old boy shot her in the head Tuesday morning, said her mother, Melissa Willey.

She died at about 11:30 p.m. Thursday, the St. Mary’s County Sheriff’s Office said. “It is with heavy hearts and great sadness we provide this update,” the sheriff’s office said in a statement.

Willey’s mother spoke to reporters Thursday evening at the University of Maryland Prince George's Hospital Center, where Jaelynn was being treated. Willey held Jaelynn's youngest sibling, who babbled as she shared the news, and her husband, Daniel, stood by her side.

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Austin Wyatt Rollins, the 17-year-old who opened fire on classmates at Great Mills High School in Southern Maryland last week, injuring one and killing another, died from shooting himself in the head, officials investigating the case said Monday. (Kevin Richardson, Baltimore Sun video)

Austin Wyatt Rollins, the 17-year-old who opened fire on classmates at Great Mills High School in Southern Maryland last week, injuring one and killing another, died from shooting himself in the head, officials investigating the case said Monday. (Kevin Richardson, Baltimore Sun video)

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Great Mills High School student Desmond Barnes, 14, and a teacher communicate with a 911 operator after a shooting at the school.

Great Mills High School student Desmond Barnes, 14, and a teacher communicate with a 911 operator after a shooting at the school.

Other family stood behind Willey as she spoke and a group of friends stood off to one side.

Jaelynn Willey was rushed to the hospital in Cheverly after the Tuesday morning shooting at the St. Mary’s County high school.

The shooting added fresh fuel to a renewed national debate about how to keep students safe from gunmen in schools. Last month, 17 students and teachers were slain at Marjory Stoneman Douglas High School in Parkland, Fla., by a gunman wielding a semi-automatic assault rifle.

Politicians have proposed new gun restrictions and measures to fortify schools.

Students from around the nation are poised to rally Saturday in Washington and elsewhere in what they’re calling the March for Our Lives.

Amid the debate, the scene in the hospital lobby was poignantly personal.

Willey said the family's lives had been altered forever.

"My daughter was hurt by a boy who shot her in the head and took everything from our lives," Willey said.

Willey, who said her daughter was the second of nine children, spoke with little obvious emotion and apologized that her baby was being loud. She said she thought it was important to share the news of the family's decision personally.

"I felt like as her mom I needed to make that statement to everybody," she said.

Supporters of Jaelynn Willey and her family set up an online page for well-wishers to provide donations. It had raised $66,000 by Thursday evening.

The family said Jaelynn was a “dedicated student” and a member of the school’s swim team.

“Jaelynn is an amazing young lady, whose peaceful presence and love of her fellow students and family is known throughout her Maryland-based school,” the family said in a statement.

Kimberly Dennis, the mother of Desmond Barnes, issued a statement earlier Thursday saying the family was grateful he was doing well. She thanked those who treated Desmond and prayed for him.

“We remain deeply saddened and shocked by this shooting incident and continue to pray for the other victim and her family during this difficult time,” Dennis wrote. “We are also praying for the entire Great Mills High School family and young people around this country.

“As a community and nation, we must continue to work and fight for a world that is safe for our children.”